Kewet Buddy City-Jet 6 Restoration

[Stefanhg]

Swapping to PureMobility CarController

I have been working toward swapping the CarController as it contains some nice improvements including a DC-DC converter for the 5V so it reduces constant current draw a lot. Now with that in mind i did repair one earlier but it threw an Error 1 code and i gave up after that. But another post mentioned it was related to the voltage measurements so i guess it is time to tackle that one now.

The way older batteries are set up is by having a wire going from each terminal of the battery to the CarController, allowing you to monitor each battery.
But when i switched to Lifepo4 i did not do anything about that and just connected +72V to CarController and then it ran. So now to restore this function you can make a voltage divider that can allow you to simulater having 6x12V batteries.

So if we do this, we can see on the left side the batteries, and on the right side the wires going to the carcontroller. Between each wire there is 12V across it which yields the same result as a 12V battery.
Now I went with a pretty low value of 1K for my application which yields an sad 12mA of constant current draw, but i don't see this as an permenent solution as i got plans later on.

One nice feature of the puremobility one is that it uses difference amplifiers in the input stage of the voltage measurements for an even lower current, but since i was unsure if the swap would go well i went with a safe value for these.

So my solution was rather.. Simple. Ad these divider resistors, hook up each voltage point of JP2 going to CarController, hook up +72V and be done.
Sadly the GND or "JP2-8 - Contact Batteries 11/12" is unconnected so I coudn't use that, so i ended up wiring into the ""JP3-7 - battery monitoring system GND"

After that, i was able to start the car without an "error 1" and could move toward using the PureMobility CarController... Except i actually realised something

For some reason the +12V is not turned on for inteior light and the high beam. So that is an ongoing investigation but currently my considered solution is bypassing the relay for that and just have it always turned on.

 

[matzetronics]

If you're using LiFePO4 cells you can tap the batteries after each 4th Cell and provide those voltages to the controller. There's no need for a voltage divider and you have the advantage of monitoring the cell voltages in real.
In my setup i use the original car controller from my El-Jet 4 (a 60V car) and provided the 12, 24, 36 48 and 60V voltages by tapping. This works like a charm.
The original car controller has an input resistance of 380kOhm on each measuring input. There are dividers by 20 on each input made with 380k/20k input dividers.

I also replaced the original linear voltage regulators on the CC board with current saving DC/DC converters. Those are very cheap these days and don't need a heat sink.

Amazon.de

In complete idle with only the car controller running, my Kewet draws below 100mA on the 60V line.

For some reason the +12V is not turned on

Could by a bad fuse or fuse holder.

 

[Stefanhg]

If you're using LiFePO4 cells you can tap the batteries after each 4th Cell and provide those voltages to the controller. There's no need for a voltage divider and you have the advantage of monitoring the cell voltages in real.
In my setup i use the original car controller from my El-Jet 4 (a 60V car) and provided the 12, 24, 36 48 and 60V voltages by tapping. This works like a charm.

I actually did consider this approach, but due to me wanting to stop relying on the shunt and CarController and instead use BMS for that, then i didn't want to go modify mine.

In complete idle with only the car controller running, my Kewet draws below 100mA on the 60V line.

That is pretty good! I think mine was at 250mA!! And swapping to the PureMobility CarController helps a lot, i still need to do some measurements of the new power consumption.

The original car controller has an input resistance of 380kOhm on each measuring input. There are dividers by 20 on each input made with 380k/20k input dividers.

Yeah i also had to reverse engineer that part, glad i have some spare CarController to look at!

Could by a bad fuse or fuse holder.

I actually did some testing yesterday. While helping another person I noticed that his Buddy didn't use the JP5 which contains the enabling of 12V relay, to my surprise it actually behaves differently on the PureMobility CarController. Here it doesn't turn on by default, which actually means the 12V for that part of the car is never turned on! I actually pulled out the CarContorller, checked wiring and indeed that was right.

One key detail I coudn't confirm was on the old CarController both NC and NO of the K5 relay was routed out to the JP5 connector as JP5-4, JP5-5 and JP6-6, on my connector in the Buddy the wires was connected on JP5-4 and JP5-5 and not JP5-6 which it is on Kewet.de

JP5-1 - ECO-Poti grinder, 5Volt = Sport, 0V = Save
JP5-2 -
JP5-3 -
JP5-4 - 12V relay input
JP5-5 -
JP5-6 - 12V relay output K4-86
JP5-7 - ECO-Poti +5V
JP5-8 - ECO-Poti GND
JP5-9 -
JP5-10 -
JP5-11 -
JP5-12 -

But one thing i saw was the JP5-6 had a trace that went to an Optocoupler around the RS-232 part like they had used the pin for something else, i coudn't see if this was just an "12V present" indicator or something else, the trace and location of optocoupler was just so odd as everything else was looking nice, but this was just routed around everything.
So currently my plan is to remove and short the relay. Saves me some constant current draw from the battery!

 

[matzetronics]

If I made this, I would just have connected IC6 diode between the two hex inverts, thus saving me one pin on the header and all the additional complexity.

Just a quick note on the display panel that this wouldn't work. The chip which is pulled low would clash with the first IC, which is always on address 0x38 (as its ADR pin is grounded). To talk to it, both selectable ICs need to get out of the way by both setting them to adress 0x3A (select inputs set high). To talk to one of those, the other needs to be set to low (then on address 0x38) and the address 0x3A is used. To talk to the other one, the action is the opposite.